For magnetic throttling between the poles of an electromagnetically operable fuel injector, usually either a nonmagnetic intermediate component is used or the seat carrier or the valve casing is equipped with a thin-walled collar as a throttle, depending on the design of the fuel injector. The magnetic circuit rapidly approaches saturation in the throttle location due to the fact that the material has a small wall thickness.
For operation of high-pressure fuel injectors, a connecting element or a supporting ring is mounted around the throttle location to mechanically reinforce the resulting mechanically weak spot.
For example, German Published Patent Application No. 195 03 821 describes a fuel injector in which the number of components of the valve tube is reduced so that the number of joints and connection points is also reduced. The entire valve tube is made of a magnetically conducting material, so that no nonmagnetic intermediate components are necessary. A thin-walled throttle point is provided between the core and the valve seat carrier.
One disadvantage of the fuel injectors described above is in particular the mechanical weakening of the valve housing or the seat carrier at the location of the magnetic throttle. Since the fuel injectors are designed mainly for direct injection of fuel into the combustion chamber of internal combustion engines having fuel mixture compression and spark ignition, high pressures prevail in the combustion chamber as well as in the fuel injector, potentially damaging the fuel injector during operation.
The connecting components normally used to reinforce the housing have the disadvantage that they must be made of a nonferritic material, independently of the internal pole and the external pole. Assembly of the connecting components may also damage the housing, which is weak at this point.